The present invention relates generally to a novel method and apparatus for anchoring a structure to or in the floor beneath a body of water. More particularly, the present invention relates to a method and apparatus for first excavating the material initially lying beneath the apparatus and then by means of hydrostatic pressure maintaining the apparatus in an anchored position in the excavation.
In the past, devices such as derricks or drilling platforms used in offshore oil well drilling operations have been anchored to the subsea floor by different methods and utilizing a variety of apparatus. For example, some derricks of the prior art utilize as an anchoring foot a conical or hemispherical shell, the open end of which is brought to rest on the underlying floor or bed of a body of water. This shell can be utilized as a cement form to mold a concrete foot which provides the primary anchoring structure.
In other instances in the prior art a "sandhogging" operation is utilized. In this sandhogging operation, an inverted shell or caisson is utilized as both a work chamber and as an anchoring foot. There is maintained a sufficient air pressure within the inverted shell or pressure chamber to keep out the water while the dirt or sand from within and at the base of the shell is removed thereby causing the structure to sink into the subsea surface and provide a secure footing.
A variety of problems may exist in these and other methods and apparatus for anchoring a structure to the floor or bed beneath a body of water. For example, in the case of devices which cement the foot to the underlying floor, there may be required relatively complicated excavation devices. Moreover, these devices may not be suitable for use in connection with sea beds having certain compositions. In addition, these types of anchoring footings may not be readily salvageable.
In instances where the sandhogging techniques and apparatus are utilized, buoyancy problems may be encountered when the inverted shell is pressurized or otherwise filled with air. In addition, in many cases a rather complex and costly airlock system may be required in conjunction with the dirt removing apparatus.
Some devices proposed by the prior art suggest an anchor for a drilling platform which is positioned over a desired location and lowered by its own weight into the subsea floor. Hydrostatic pressure is used to provide additional force to drive the anchor into the subsea floor. It is apparent, however, that such devices may have limited usefulness determined by such factors as the composition of the subsea floor.
It is therefore a general object of the present invention to minimize the problems of the type previously noted which exist in the prior art.
A more particular object of the present invention is to provide a novel method and apparatus for anchoring a structure to a floor of a body of water which substantially eliminates the necessity of utilizing shovel-type excavating equipment.
It is another object of the present invention to provide a novel method and apparatus for anchoring a structure to a floor of a body of water which substantially eliminates the necessity of utilizing a cementing operation to achieve a suitable anchor.
It is yet another object of the present invention to provide a novel method and apparatus of anchoring a structure to a floor of a body of water which utilizes a movable jet to excavate the floor beneath a body of water.
It is a further object of the present invention to provide a novel apparatus for anchoring a structure to a floor of a body of water which apparatus utilizes hydrostatic pressure to assist in firmly securing the footing apparatus in position.